1. Field of the Invention
The present invention relates to a thin film primary cell utilizing a solid polyelectrolyte.
2. Related Art Statement
According to the JIS (Japanese Industrial Standard), conventional primary cells are broadly classified into three groups: manganese dry cells (JISC8501-1984), alkaline primary cells (JISC8511-1985) and manganese dioxide lithium primary cells (JISC8512-1982). The latter two primary cells have increasingly become universally used in various applications as button- or coin-shaped thin cell power sources for cameras, electronic calculators, IC cards, etc.
Typical electrolytes employed in these prior art primary cells include: zinc chloride used in manganese dry cells; potassium hydroxide used in alkaline primary cells; and organic electrolytes and thionyl chloride used in manganese dioxide lithium primary cells. However, all such primary cells have a serious safety problem because all of the above electrolytes are liquid and therefore susceptable to leakage.
Moreover, primary cells of the types described above are constructed to seal in the liquid electrolyte and the requirement for such liquid seals has limited reduction of thickness of such cells. Because of that limitation, it remains impossible to reduce the thickness of the battery to 0.05 mm or less. A thickness of 0.05 mm or less is desirable in batteries for liquid crystal displays, watches, electronic calculators, IC cards, earphone radios, music box cards, temperature sensors, hearing aids, electronic floats for fishing, electronic thermometers, IC lighters, LEDs, pressure-sensitive buzzers, etc. in which conventional thin cells are employed.
Cells having a solid polymeric electrolyte are described in U.S. Pat. No. 4,556,614 but the thickness of the described cells is in excess of 0.05 mm. Those cells are of a fixed shape and have no flexibility. Accordingly, the scope of their usefulness is limited.